Enzymes of pyrimidine metabolism in the musculus complexus of the chick during development.

The pattern of cytidylate and uridylate phosphatase, uridine phosphorylase, cytidine and cytosine deaminase activities has been studied in M. complexus during chick development. The comparison of these enzyme activities with thigh muscles ones has shown that quantitative and temporal changes occur, in parallel with the unusual pre-natal and early post-natal development of M. complexus. The results suggest that during the first period of incubation, UMP might follow the anabolic pathway UMP-UTP, which leads to cytidine nucleotides, while approaching the hatching, the catabolic pathway should prevail. In addition, immediately after hatching, pyrimidine metabolism is especially supported by cytidine nucleotides.     

Purification and properties of myosin from the "hatching muscle" (m. complexus) of geese

The present work is concerned with the study of myosin fractions prepared from the hatching muscle (m. complexus) and a control muscle (m. pectoralis) of the developing goose embryo. The m. complexus attained its maximum mass at hatching and in the 4-day-old bird the mass of this muscle was only one fourth of that recorded at hatching. The m. complexus was hypertrophied already on the 21st day. At days 21, 27 and 28 of incubation and at posthatching days myosin preparations were made from both muscles. Partial purification of myosins from both sources yielded a high molecular weight fraction characteristic of the adult bird and one other protein fraction with molecular mass half of myosin. Both preparations exhibited the characteristic properties of myosin. The lower molecular weight fraction was also shown to develop filamentous aggregates as did the higher molecular-weight, gel filtrated myosin. The phosphate content of the half molecular mass myosin fraction prepared from the embryonic m. complexus at days prior to hatching was considerably higher than that of the high molecular weight fraction and the predominant component was P-Arg. Since the embryonic myosin was still not available in the m. complexus of the 4-day-old birds and the hypertrophied muscle underwent regression after hatching it appears that this myosin fraction is actively involved in breaking through the shell during the hatching period in geese.     

Effect of steroids on definitive localization of primordial germ cells in the chick embryo.

It has been suggested that PGCs are attracted to developing gonads by a chemotactic-like agent secreted by the gonads and that this agent might be steroidal in nature. This study was undertaken to ascertain whether specific exogenous steroid hormones exert an influence on germ cell colonization of the gonads, by enhancing, inhibiting or otherwise interfering with it. Testosterone cypionate in cottonseed oil, crystalline testosterone propionate, estrone in aqueous suspension and crystalline estradiol-17beta were adminstered to chick embryos at 33 hours incubation. Normally developed embryos, those receiving cottonseed oil (vehicle for testosterone cypionate) and those receiving cholesterol served as controls. A decrease in the number of germ cells in the gonadal area at five days of incubation occurred in all groups receiving the androgens and estrogens. However, in only one group (that receiving testosterone cypionate) was this decrease found to be significant. The mean number of germ cells found in the cottonseed oil controls and the cholesterol controls closely paralleled that of the normally developed controls. Normal asymmetry in the distribution of the germ cells favoring the left side in the chick was not affected in any of the groups; however, the percentage distribution of the germ cells between the right and left gonads at this early stage appeared to be affected.     

Yolk steroids and the development of the hatching muscle in nestling European Starlings

Hatching asynchrony in avian species often leads to the establishment of a size hierarchy among nestlings. Because the youngest nestlings in a brood are often at a significant disadvantage with respect to competition for parentally‐delivered food, one might expect to find that mechanisms have evolved to alleviate the detrimental effects of hatching asynchrony and enhance the survival of last‐hatched offspring. The musculus complexus, or hatching muscle, is responsible for breaking the shell during hatching and for dorsal flexion and extension of the neck during begging. An increase in its strength in last‐hatched nestlings could therefore reduce the duration of hatching or enhance the ability to beg for parentally‐delivered food, thereby enhancing the competitive abilities of those nestlings. I previously found in the Red‐winged Blackbird Agelaius phoeniceus that the mass of the complexus increases with laying order and that its development is mediated by the actions of yolk testosterone. I investigated the hypothesis that yolk steroids also affect the development of the complexus in the European Starling Sturnus vulgaris. I asked, first, whether the mass of the complexus increases with laying order and, if so, whether this increase is at least partially attributable to a corresponding increase in the concentration of yolk testosterone. Because exogenous progesterone increases the water content of the complexus in the domestic fowl Gallus gallus I also asked whether an increase in complexus mass, if present, could be partially attributable to an increase in progesterone concentration across the laying order. I found that both yolk testosterone concentration and the mass of the complexus increased with laying order; however, there was no variation in the concentration of either yolk progesterone or the proportion of water in the complexus across the laying order. There were no differences in the concentrations of either androstenedione or 5α‐dihydrotestosterone across the laying order.     

Enzymes of purine metabolism in the nuchal muscle (M. complexus) of chick embryo]

The developmental patterns of enzyme activities related to GMP metabolism have been investigated in chick embryo musculus complexus (m. Complexus). Guanylate phosphatase activity increases conspicuously from 18th to 21st day, guanosine phosphorylase increases on the 21st day and the guanase shows a very low activity during the whole period considered. Xanthine oxidase was always found absent. The results suggest that during the first period of incubation GMP breakdown in chick embryo m. complexus might follow a catabolic pathway, while starting from the 18th day some guanine might be converted to GMP originating a new metabolic pathway as previously suggested for AMP metabolism.     

An evaluation of systems for paper chromatography of C21 steroids.

A group of moderately polar C21 steroids (3-5 oxygen functions) has been chromatographed in 9 solvent systems. Using the concept that standard deviation of the mean RF is an index of chromatographic resolution, and that coefficients of correlation between sets of RF data can be used to quantify the similarities of chromatographic systems, we have evaluated the resolving properties of the systems when used individually, and also when used in combinations of two, three and four. The discriminating powers of some of the most effective individual systems, and some of the sequences of systems which are most efficient, are shown graphically as chromatography trees. The relationship between the total effective standard deviation of a group of systems which are used in sequence and the probability that a pair of compounds will be separated by more than 0.10 RF is discussed.